Substantial effort and attention continue toward the development of newer and more sustainable energy supplies. The conservation of energy by increased energy efficiency remains crucial to the world's energy future. According to an October 2010 report from the U.S. Department of Energy, heating and cooling account for 56% of the energy use in a typical U.S. home, making it the largest energy expense for most homes. Along with improvements in the physical plant associated with home heating and cooling (e.g., improved insulation, higher efficiency furnaces), substantial increases in energy efficiency can be achieved by better control and regulation of home heating and cooling equipment. By activating heating, ventilation, and air conditioning (HVAC) equipment for judiciously selected time intervals and carefully chosen operating levels, substantial energy can be saved while at the same time keeping the living space suitably comfortable for its occupants.
It would be beneficial, at both a societal level and on a per-home basis, for a large number of homes to have their existing older thermostats replaced by newer, microprocessor controlled “intelligent” thermostats having more advanced HVAC control capabilities that can save energy while also keeping the occupants comfortable. To do this, these thermostats will need more information from the occupants as well as the environments where the thermostats are located. Preferably, these thermostats will also be capable of connection to computer networks, including both local area networks (or other “private” networks) and wide area networks such as the Internet (or other “public” networks), in order to obtain current and forecasted outside weather data, cooperate in so-called demand-response programs (e.g., automatic conformance with power alerts that may be issued by utility companies during periods of extreme weather), enable users to have remote access and/or control thereof through their network-connected device (e.g., smartphone, tablet computer, PC-based web browser), and other advanced functionalities that may require network connectivity.
Among other requirements, the successful implementation of intelligent network-connected thermostats into widespread, practical everyday use in a large number of homes and business requires the deployment of computers, networks, software systems and other network infrastructure capable of providing the necessary provisioning, data management, and support. Data communications methods between the intelligent thermostats and centrally provided management servers (which can also be termed “cloud-based” management servers), needs to be responsive, robust, and scalable. At the same time, however, the hardware and methodologies employed need to be compatible with, and workable in view of, a large installed base of conventional routers and network services that are already in homes and business, such that widespread adoption of the network-connected intelligent thermostats be commercially feasible.
One further issue that arises with thermostats relates to the limited external electrical power that is made available to the thermostat in many homes and businesses. As known in the art, for some installations, electronic thermostats can be powered directly from an HVAC system transformer by virtue of a 24 VAC “common” wire (“C-wire”) that runs from the HVAC transformer to the thermostat. When provided, the C-wire has the particular purpose of supplying power for an electronic thermostat. However, many HVAC installations do not have a C-wire provided to the thermostat. For such cases, many electronic thermostats have been designed to extract electrical power by a scheme called “power stealing,” “power sharing” or “power harvesting,” in which power is tapped from the HVAC control wires that lead to the HVAC call relay coils. Such thermostats “steal,” “share” or “harvest” their power during the “OFF” or “inactive” periods of the heating or cooling system by allowing a small amount of current to flow through it into the call relay coil below its response threshold. During the “ON” or “active” periods of the heating or cooling system the thermostat can be designed to draw power by allowing a small voltage drop across itself. The amount of instantaneous electrical power that can safely be supplied by power stealing methods without falsely tripping or un-tripping the HVAC call relays is generally quite limited. These limitations can, in turn, can severely restrict the processing and network communications capabilities that can be provided on a power-stealing thermostat.
It would be desirable to provide a microprocessor controlled intelligent thermostat having advanced HVAC control capabilities that can save energy while also keeping the occupants comfortable. It would be further desirable to provide a such a thermostat that is network-capable. It would be even further desirable to provide a cloud-based thermostat management infrastructure to facilitate the provisioning, data management, and support of a large number of such network-connected intelligent thermostats. It would be still further desirable for such intelligent thermostats to be capable of such advanced processing, HVAC control, and networking functionalities while at the same time being capable of being powered by power-stealing, whereby a C-wire or household wall outlet power is not required, so that the thermostat is compatible with a broad array of practical HVAC installations in homes and businesses. It would be even further desirable to provide a network communications architecture, methodology, and protocol for facilitating data communications between the cloud-based management server and such intelligent network-connected thermostat. It would be still further desirable to provide such a thermostat and cloud-based management server in a way that is compatible with a large installed base of conventional routers and network services. Other issues arise as would be apparent to a person skilled in the art in view of the present disclosure.